/**
 * Created with IntelliJ IDEA.
 * Description:温度转换
 * User: zjc
 * Date: 2022-06-01
 * Time: 22:53
 */
import java.util.Scanner;
public class Main{
    public static void main(String[]args){
        Scanner in = new Scanner(System.in);
        double input = in.nextDouble();
        System.out.println(String.format("%.3f",(double)5/9*(input-32)));
    }
}
